The present invention relates to a traffic control system and more particularly to a system that can automatically determine appropriate speed limits at various locations.
It is well known that many people are injured annually as a result of motor vehicle crashes in construction work zones, and many of those injuries result in fatalities. Drivers not paying attention and excessive speed are the leading factors in these accidents, over 40% of which happened in the transition area before the construction work zone. The transition from high speed, open road traffic to reduced speeds at points of traffic congestion and construction sites, etc., can result in rapid deceleration or rear end accidents, and uneven traffic flow, while reducing capacity and possibly enabling unsafe speeds in construction work zones.
The prior art has attempted to solve this problem by the use of portable light signalling equipment. Such portable light signalling equipment has been used for both regulating traffic at restricted points and as a replacement for defective stationary equipment. Frequently, it is observed that movable traffic lights of this kind, which are required at building sites, for example, are not optimally adapted to the traffic flow, and as a result cause unnecessary delays to much of the traffic, particularly when the traffic flow is fluctuating. Generally, conventional portable light signalling equipment includes equipment that does not have any optional feedback system. The xe2x80x9cstopxe2x80x9d, xe2x80x9cgoxe2x80x9d and clearance times are pre-programmed and are usually only very broadly adapted to the actual traffic, and are invariant in their daily operation. Centrally controlled and monitored equipment, with passive light signalling equipment, allows the signal to be set by feedback. However, such equipment requires expensive cabling, the size of which has to be adapted to the power (including the current supply to the lights) to be transmitted. For example, U.S. Pat. No. 6,124,807, issued Sep. 26, 2000, to R. Heckcroth et al, provides a procedure for regulating traffic by means of movable light signalling equipment. The movable signals are placed at restricted areas, and use sensor controls to prescribed xe2x80x9cgoxe2x80x9d times and clearance times in the area to be secured (i.e., along a blocked stretch). The transit time of vehicles, over a measured distance extending substantially along the blocked stretch, is measured and the clearance time is established as a function of the transit time measurements obtained.
It is also known to use an apparatus for controlling two traffic lights at either end of a work zone. Axle counters are provided that switch the apparatus over by means of counters whenever there is a coincidence between two counting circuits (i.e., when the number of the counted vehicles leaving the restricted area equals the number of the vehicles that entered the area). However, there can be malfunctions if vehicles remain in the restricted area, or enter the restricted area outside of the surveillance points. In such cases, the equipment has to be restarted. Moreover, such equipment does not provide separate xe2x80x9cgoxe2x80x9d and clearance times. For example, U.S. Pat. No. 5,900,826, issued May 4, 1996 to Farber, discloses a signalling system for controlling two-way traffic flow around a construction zone. The system consists of two traffic lights at opposite ends of a construction zone that are alternately activated to give a green light to oncoming traffic. The lights communicate through a wireless link. The lights are also provided with sensors that detect whether a vehicle is attempting to go through on a red light. When such a vehicle is detected, an audible warning signal is activated.
In another prior art system, traffic signals and detectors, e.g., pressure sensors at both ends of a restricted section, are provided for detection of the number of vehicles passing through. The signalling time of green signals is extended at the heavier traffic end. A signal controller circuit includes a signal device that changes the signal indication by means of vehicle detector, e.g., light sensors or the like, provided adjacent to the signals. Further, a system is known for an alternately switched traffic signal controller having a set of traffic signals which are operated such that while one traffic light at the xe2x80x9cpassage allowedxe2x80x9d end is green, the other traffic signal at the xe2x80x9cno passage allowedxe2x80x9d end is red, or against. Detectors are provided for detection of vehicles passing through the section. Furthermore, a traffic signal device is also provided at both ends of a road section under construction. In such systems, the waiting time is still comparatively long, thus easily causing traffic jams when traffic density is distinctly larger at one side than at the other side in the road repairing section.
In addition, sensitive systems have been employed for control of the lighting of the traffic signals based on the detection of vehicles by the detector, e.g., pressure sensors, light sensors or the like. The control systems for traffic signals can be damaged in case of troubles in the detector means. Furthermore, as such signal systems are usually still in operation even at night when no vehicles are present, there is sometimes no input of detection signals for more than a pre-set time. In such a case, it cannot be concluded merely from the fact of no traffic that the detector means are out of order. Additionally, vehicles from the opposite directions can be exposed to great danger of head-on collision in the case that a vehicle enters the section against a red signal immediately after the change to red from green, while another vehicle also enters the section because of the signal change to green from red before the passing of the opposite vehicle.
Portable traffic control systems that are particularly suited to controlling traffic in work areas have also been disclosed. Normally, the systems are used on roads that have two traffic lanes, each for traffic in a different direction. When repair work is being performed on one lane of the road, however, the traffic in both directions must use the other lane. The control systems employ traffic lights at each end of the traffic lane, alternately presenting a xe2x80x9cgoxe2x80x9d signal first to traffic from one direction and then to traffic from the other direction. The signals are viewable not only by oncoming traffic but also by an operator standing between the display units.
Another known device is intended to alert work zone personnel when a vehicle enters the work zone. This device is configured to detect the intrusion of a vehicle into the work zone along any section of the work zone perimeter adjacent to an active traffic lane. An infrared source is placed at the beginning of the work zone, which transmits a continuous wave infrared signal along the perimeter of the work zone for reception by an infrared detector positioned downstream. If a vehicle passes between the source and the detector, thereby interrupting the continuous wave infrared signal which is transmitted therebetween, the detector acknowledges this obstruction by sounding an alarm. However, this device also suffered numerous problems in operation.
This device suffers from several integrity problems. The heat and audible noise produced by work zone equipment, passing traffic, and other conditions of the work zone environment is capable of interfering with the infrared or ultrasonic detectors in such a way that the detectors can fail to detect a vehicle passing through the detection beam. Because the detector is designed to sense the presence or absence of a reflected detection beam, the detector is susceptible to detecting the heat or noise produced in the work zone as the reflected detection beam, even when the detection beam is obstructed by a vehicle entering the work zone. This is particularly true where the detector employs a continuous infrared signal. Thus, the potential always exists for a vehicle to pass through the detection beam without sounding the alarm, and without any warning to the work zone personnel.
Additionally, airborne particulate matter, birds, precipitation, and drifting debris can sporadically interrupt the constant signal or beam transmitted by the detector, thereby causing false detections, which results in a loss of credibility for the device and costly work stoppages. Further still, the distance between the detector and the siren necessitates a wireless data link therebetween (which itself require FCC approval).
Secondly, because a continuous wave infrared signal is employed, filters cannot be used in the receiver to remove low frequency infrared noise without also removing the infrared signal to be detected. Nor can filters be used in the receiver electronics to remove electromagnetic noise emanating from sources within or proximate to the work zone. The range of the device is therefore unduly limited, as the detector can not be placed more than 230 m. from the infrared source and still reliably distinguish the continuous infrared signal from other infrared energy present in the work zone. Given that typical roadway work zones have a length well in excess of 230 m., an unacceptably large number of infrared sources and detectors has to be used in order to detect breaching vehicles along the entire perimeter of the work zone adjacent to active traffic lanes. Moreover, because the infrared source has to transmit a focussed and narrow beam in order to have a detectable range of 230 m., the infrared detector has to be precisely positioned in the line of sight of the infrared source to receive the transmitted beam. The infrared detector is therefore difficult to set up and align along the work zone perimeter, and is not amenable to being moved frequently from work zone to work zone. This lack of portability is further amplified where numerous infrared sources and detectors have to be employed. The infrared detector can also be fooled into detecting a stray infrared signal as the constant infrared beam so that a vehicle can pass into the work zone undetected. Further still, this device, like all other prior art devices, employs an audible alarm for signalling personnel of an errant vehicle.
In addition, currently, systems used in controlling traffic conditions around work zones and incidents on the road are limited to the use of conventional static signs, flashing arrow signs, portable variable message signs (VMS) which are programmed with a single repeating message, or no signs at all. These systems provided little or no information which is useful to drivers, either for avoiding the development of a traffic jam or for finding alternative routes. Though portions of the highways close to large metropolitan areas are often equipped with permanently installed VMSs and traffic signal lights designed to control the in-flow or out-flow of traffic in the highways, there are large stretches of highways that lack any facilities for controlling the flow of traffic on the highway that are usable around work zones or incidents on the road. Rather, the same conventional equipment as described above is used and provides the same limited information to drivers. Even if permanently installed VMSs were available, current methods in the use of such devices also provide very limited information for drivers in avoiding traffic jams due to the presence of work areas and/or roadside incidents. Such information is not credible because the messages they convey is typically not appropriate to existing conditions.
Further examples of prior art traffic advisory and monitoring systems include U.S. Pat. No. 6,064,318, issued Jan. 16, 2000 to Kirchner III, et al. Kirchner discloses a portable traffic advisory system that monitors current traffic conditions in the vicinity of a construction zone or accident. This system is mainly intended to provide real time traffic information to motorists. Thus, this patent is directed to a portable system for automatic data acquisition and processing of traffic information in real-time. The system incorporates a plurality of sensors which are operatively positioned upstream of a work zone or roadway incident with each of the sensors being adapted to detect current traffic conditions. At least one variable message device is positioned upstream of the work zone or roadway incident. A plurality of remote station controllers are provided, each being operatively connected to the plurality of sensors and to the variable message device. A central system controller is located within remote communication range of the remote station controllers. The central system controller and the plurality of remote station controllers are capable of remotely communicating with one another. Each of the sensors is adapted to output traffic condition data to its corresponding remote station controller. The corresponding remote station controllers then transmits the traffic condition data to the central system controller. The central system controller automatically generates traffic advisory data based on the traffic condition data and transmits the traffic advisory data to the remote station controller that is connected to the variable message device. The traffic advisory data can also be used to communicate with and control highway advisory radio transmitters and ramp metering stations. One or more variable message devices, highway advisory radio transmitters and ramp metering stations are used to inform passing motorists of traffic conditions in and around a work zone or roadway incident, and thereby to control and improve the safety and efficiency of traffic operations around such sites. This traffic advisory data is limited to providing advisory information such as xe2x80x9cReduce Speed Aheadxe2x80x9d, and cannot provide legally enforceable speed limit changes.
U.S. Pat. No. 5,729,214, issued Mar. 17, 1998 to Moore, discloses a traffic signalling system that consists of roadside sensors for detecting traffic conditions, weather conditions, etc., a central processing station to which the detected conditions are transmitted and processed, and signals controlled by the central processing station in response to the detected conditions. This system permits dynamic monitoring of traffic conditions, and selective display of messages to motorists depending on the conditions. This is a particularly complex system employing satellite communication of the detected conditions to a remote central processing stations.
U.S. Pat. No. 5,673,039, issued Sep. 30, 1997 to Pietzch et al, discloses a traffic and road condition monitoring system that can be disposed along a roadway. The system includes multiple traffic and/or load-sensing sensors arrayed along the road to detect vehicle speed, traffic conditions, traffic violations, lane occupancy, etc. The processed output from the sensors controls a series of flashing lights and/or alpha-numeric displays in accordance with the detected conditions. The patent thus provides an arrangement for monitoring vehicular traffic and providing information and warnings to drivers of traffic disruptions, driver error, dangerous road conditions, and severe weather.
U.S. Pat. No. 5,610,599, issued Mar. 11, 1997 to Nomura, discloses a traffic signal control system for use in bi-directional flow control around a construction zone. The system consists of traffic lights at either end of the construction zone attached to a central controller. Sensors, e.g., pressure sensitive strips, are located at both ends of the construction zone and are attached to the controller. Each light is programmed with a minimum and maximum green light time. The light is initially activated for the minimum time. If heavy traffic is detected, the green light is extended for further incremental periods until the maximum time is reached.
U.S. Pat. No. 5,542,203, issued Aug. 6, 1996 to Luoma, provides a mobile sign with a solar panel for warning motorists of highway problems. The mobile sign comprises a wheeled vehicle, an electrically powered sign panel mounted on the wheeled vehicle, a chargeable battery for powering the sign panel, and a solar panel for charging the battery. The solar panel is rotatable and tiltable relative to the wheeled vehicle. The sign panel is independently rotatable relative to the wheeled vehicle.
U.S. Pat. No. 5,257,020, issued Oct. 26, 1993, to Morse, provides a moveable traffic signalling, which includes a trailer having wheels and a supporting structure. A general purpose message board is supported by the supporting structure of the trailer, for communicating to drivers of passing vehicles a user-selected alpha-numeric message. An operator interface is mounted on the supporting structure, for programming the message to be displayed at the site. A controller interacts with the operator interface to provide the programmed message to the message board.
U.S. Pat. No. 4,857,921, issued Aug. 15, 1988, to McBride et al, provides a digital control system for controlling the flow of traffic in selected directions in response to digital signals that are transmitted from a common transmitting control unit to multiple separate receiving traffic control units respectively associated with each controlled direction. The transmitting unit includes a transmitter and digital command code generator operative, when actuated, to transmit a character in the form of a digital signal specific for one of the receiving units. Each receiving unit includes traffic control indicators which are operative in different modes to display indications visible to traffic flowing in the direction to be controlled by that unit. Each receiving unit further includes a receiver operator to deliver demodulated characters based on codes which are transmitted by the transmitting unit. The codes control a microprocessor which is programmed to process the received characters to initiate command outputs. Logic circuitry is connected to receive the outputs. Responsive thereto, traffic control indications are displayed as determined by the local units demodulated characters. Each keeps a model of that which is displayed by other units in the system, and uses it to prevent conflicting traffic control indications.
None of the above systems provide a simple, reliable, traffic control system that monitors and controls vehicle speed through a work zone, or around an accident. It is, therefore, desirable to provide a variable work zone speed controller and system that can collect information related to vehicle speeds and traffic density in the work zone, and signal drivers appropriately.
It is an object of the present invention to obviate or mitigate at least one disadvantage of previous traffic regulation systems and controllers. It is particularly desirable to provide a system for traffic control that assures smooth flow through and around a road section under construction; improves safety of traffic flowing through and around a road section under construction; provides useful information to travellers in vehicles flowing through and around a road section under construction; automatically determines appropriate speed limits at various locations within a road section under construction; displays the current speed; provides relevant speed limits for existing traffic and site conditions within a road section under construction; enables smooth deceleration from highway speeds within a road section under construction; and enables uniform traffic speed within a road section under construction.
In a first aspect of the present invention, there is provided a variable speed limit controller. The variable speed limit controller is for communicating with a traffic station to determine a speed limit based upon input provided by a sensor in the station, and with a display for displaying a variable speed limit. The controller comprises an input, an output and a processor. The input is for receiving information related to lane occupancy and at least one of traffic flow, road conditions, vehicle speed, vehicle presence and weather conditions, from the sensor. The output is for transmitting a derived speed limit to the display. The processor is for receiving the information from the input, for determining the derived speed limit for a region adjacent to the station, based on the received information, and for providing the derived speed limit to the output for transmission to the display.
In an embodiment of the first aspect of the present invention the processor includes means for inversely varying the speed limit in accordance with lane occupancy information. In another embodiment of the present invention the input includes means for receiving information from a plurality of sensors located in a plurality of stations spaced apart from each other, the processor optionally includes means for deriving a speed limit for each station, based on the information received from the sensors located in each station, and the output optionally includes means for transmitting the plurality of derived speed limits to a corresponding plurality of displays. In a further embodiment of the first aspect the output includes means for transmitting the derived speed limit to the display using a wireless communications channel. In a presently preferred embodiment, the wireless communications channel is an RF communications channel.
In another embodiment of the first aspect of the present invention the processor includes means to derive a text based message, for transmission to the display by the output, the message derived using the information received from the input. In a further embodiment, the display includes means for displaying the derived text based message in addition to the derived speed limit. In another embodiment, the output includes a wireless modem to transmit output signals to a monitoring station, where the monitoring station can be selected from a list including a personal computer and a pager. In a presently preferred embodiment, the wireless modem is a cellular communication modem.
In a further embodiment of the present invention, the sensor is selected from a list including active radar sensors, passive acoustic sensors, ultrasonic sensors, pneumatic road hoses, tape switches, piezoelectric sensors, fibre optic sensors, quartz sensors, active magnetic devices, inductive loops, elongated elastomeric members having an elongated pressure sensor thereon, coaxial piezoelectric cables, flanged tube sensors with piezoelectric plates, and DYNAX(trademark) sensors.
In another embodiment of the present invention, the variable speed limit system controller includes means for connecting a power supply to provide power to the input, the output, and the processor. In a further embodiment, the power supply includes a solar panel array. In other embodiments of the present invention, the processor includes means for determining the speed limit using a lookup table and the received information, and means for determining the speed limit using a lookup table, the received information, and time of day information.
In yet another embodiment of the present invention, the variable speed limit system controller includes a refresh engine for initiating a refresh of the derived speed by the processor, which optionally includes means for initiating the refresh at fixed intervals. Alternatively, the refresh engine can include means for initiating the refresh at intervals determined by the received information. In other embodiments of the present invention, the processor includes means for manually overriding the derived speed limit, and for providing a static speed limit and text message to the display.
In a further embodiment of the present invention, the variable speed limit system controller includes a self diagnosis engine for verifying that the operation of the input, the output and the processor are within predefined tolerances. In a further embodiment, the self diagnosis engine further includes means for entering a fail safe mode of operation when a component outside of the predefined tolerance is detected. In another embodiment of the present invention, the received information related to road conditions includes information regarding whether the road surface is dry, wet, icy or frost covered.
In another embodiment of the present invention the processor includes means for deriving general advisory messages based on the received information and for providing the derived general advisory messages to the output for transmission to the display.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.